Grid resistance



May 31, 1932. H. E, CAMPBELL GRID RESTSTANGE Filed Jan. 2l, 1929 vivre..

.549. 4 valant... ,2.5 A.

mu A TTORNEYS QW/5 A Patented May 31, 1932 UNTE STTES PATENT oFFlcE.

HARRY E. CAMPBELL, OF MILWAUKEE, WISCONSIN, ASSIGNOR, BY MESNE ASSIGN-MENTS, TO CUTLER-HA1VI1VIER, INC., A CORPORATION OF DELAWARE GRIDRESISTANCE Application led January 2l, 1929. Serial No. $33,900.

rlhis invention relates to improvements in grid resistances moreparticularly adapted for use with electric controllers and starters ofvarious kinds.

It is one of the objects of the present invention to provide a gridresistance formed of cast iron or other metal in which each resistancegrid or element consists of a number of parallel strips of thin metalconnected together in staggered relation at their ends by return bendsto provide a continuous length of material having slotted attaching lugsat its opposite ends.

A further object of the invention is to provide a grid resistance havingmeans for maintaining assembled grids in position even though the gridholding members have become loosened.

A further object of the invention is to provide a grid resistance inwhich the grids when assembled in a bank are interlocked together insuch a manner as to rigidly hold the grids together and form electricalcontacts between pairs of terminal lugs to provide a continuouscircuit'from one end of the bank to the other.

A further object of the invention is to provide a grid resistance whichwhen assembled in a bank, individual grids may be removed or replacedwithout disturbing the other grids of the bank.

A further object of the invention is to provide a grid resistance whichis of simple construction, is strong and durable and is well adapted forthe purpose described.

With the above and other objects in view, the invention consists of theimproved grid resistance and its parts and combinations as set forth inthe claims, and all equivalents thereof.

In the acompanying drawings in which the same reference charactersindicate the same parts in all of the views:

Fig. 1 is a longitudinal sectional view of a bank of the grid resistanceunits taken on line 1--1 of Fig. 2;

Fig. 2 is a transverse sectional view thereof taken on line 2-2 of Fig.1; and

Fig. 3 is a top view of the grid resistance bank, the supporting framebeing broken away.

Referring to the drawings the reference numeral 5 indicates sheet metalframe members of rectangular 'form and provided with reinforcing flanges6 having openings formed therein for attachment to a support. T he framemembers are spaced apart and are connected together by horizontallyextending spaced rods 8 which extend through the frame members and areadjustably connected thereto by nuts 9. The nuts are threaded on therods on each side of each frame member to rigidly clamp the rods theretoas clearly shown 1n Fig. 1. Portions of the rods between the framemembers are enclosed in insulating tubes 10 and the terminal lugs 11 and11 of cast iron grids 12 and 12 extend partly around said insulatingtubes 10. Each upper grid consists of a pair of terminal lugs 11 havingalined slots 13 which open edgewise in the same direction as shown inFig. 2. The `lugs of each upper pair are connected together by a thinstrip of metal 14 of serpentine shape in which the parallel portions 15of the strip lte joined together by return bend portions The lower grids12 are of the same shape as the upper grids and have strips 14, parallelportions 15 and return bends 16', and said strips 14 are connected toterminal slotted lugs 11 in the same manner as the upper strips and lugsare connected together. Each slotted lug is thicker than the stripportion 'and projects outwardly laterally on both sides of the strip toform shoulders 17 of circular shape. Washers 18 having annular laterallyprojecting shoulders 19 are mounted on the insulating tubes 10 betweenalternate adjacent lugs, and the annular flanges 19 of said washersextend over the annular shoulders 17 of the adjacent lugs 11 to preventthe accidental removal of the grids in the Lvent that the nuts 9 shouldbecome loosene Washers 20 and 21 and a spacer tube 22 mounted on theinsulating tube 10 and interposed between the frame members and theopposite sides of the bank of grids provide for clamping the gridmembers in position by means of the inner nuts 9 and when thus tightenedthe outer nuts 9 are then threaded firmly against the frame members toclamp the rods to said members and to lock the inner nuts in position.

To provide a circuit through all of the grids from one end of the bankof upper and lower grids to the other, insulating washers or disks 22are interposed between alternate pairs of slotted lugs and said washersare staggered with relation to the insulating washers 22 mounted on theopposite rodl 8.

Terminal connector posts 23 mounted on one of the rods and on the outersides of the two end grids of the bank provide for connecting electriccircuit wires 24 thereto. As thus connected, referring to Fig. 3, thecurrent will flow rearwardly from the left hand terminal 23 through thelower grid 12 which is connected to the upper grid 12 and then forwardlythrough the said upper grid to `the next adJacent lug which forms partof the next lower grid and thus back and forth to the right handterminal member 23.

Particular attention is directed to the fact that the lugs of a gridextend inwardly toywards each other so thatthe outer edges of the lugsare substantially flush with the outer edges of the outer parallelportions or legs of the grid strip to form a compact structure.Furthermore the lugvslots 13 open edgewise in the same direction topermit the easy revmoval of any one of the grids when the nuts have beenloosened suliiciently to permit the lug lshoulders 17 to disengage thewasher flanges 19.

The invention also contemplates the use of two or more grids placedtogether and the connecting and insulating the lugs of connected pairsof grids to provide greater current capacity.

From the foregoing description it will be seen that the grid resistanceis of very simple construction and is well pose described.

y What Iclaim as my invention is:

1. vThe combination with a grid resistance and supporting means thereforincluding a rod, said grid having a lug with an open slot to receivesaid rod, of a member loosely mounted on said rod and movable relativelyadapted for the pur- 4to said lug into and out of interlockingengagement therewith, said-member when in Vinterlocking engagement withsaid lug affording said lug additional securement to saidrod.

` 2. A grid resistance, comprising insulated rods, resistance units ofgrid formation having" inwardly projecting slotted lugs which extendpartly around the insulation of the rods, said lugs having laterallyextending shoulders, flanged washers interposed between-some' of theAlugs and engaging the shoulders to preventaccidental removal ofthergrids, the slots of said lugs opening in one direction, insulating'washers interposed between alternate pairs of lugs on each rod,

the insulating washers between lugs on one rod being staggered withrelation to the interposition of the insulating washers on the otherrod, terminal members for the bank of grids, and threaded means forclamping the lugs and the washers and the terminal members rigidlytogether.

3. A grid resistance, comprising insulated rods, resistance units ofgrid formation having inwardly projecting slotted lugs which extendpartly around the insulation of the rods, said lugs having laterallyextending annular shoulders, washers interposed between some of the lugsand having laterally extending annular flanges which overlap the annularshoulders to prevent accidental removal of the grids, the slots of saidlugs opening in one direction, insulating washers interposed betweenalternate pairs of lugs on each rod, the insulating washers between lugson one rod being staggered with relation to the interposition of theinsulating washers on the other rod, terminal members for the bank ofgrids, and threaded means for clamping the lugs and the Washers and theterminal members rigidly together.

ll. A grid resistance, comprising frame members, spaced rods connectedthereto, insulating tubes extending around said rods between the framemembers, resistance units of grid formation having slotted lugs whichextend partly around the insulation on the rods, said grids beingalternately positioned above and below the rods and said lug slotsopening in one direction, said lugs having laterally extending annularshoulders, washers interposed between some of the lu s and havinglaterally extending annular anges which overlap the annular shoulders toprevent accidental removal of the grids, insulating washers interposedbetween alternate pairs of lugs on each rod, the insulating washersbetween lugs on one rod being staggered with relation to theinterposition of the insulating washers on the other rod, terminalmembers for the bank of grids, and nuts threaded on the rods forclamping the lugs and the washers rigidly together.

5. The combination with a grid resistance and supporting means thereforincluding a rod, said grid having a lug with an open slot to supportsaid grid on said rod, of a member surrounding said rod and movablealong the latter into an interlocking relation with said lug to locksaid grid against removal from said rod.

6. The combination with a grid resistance and supporting rods therefor,said grid having lugs with open slots for engagement with said rods, ofmembers surrounding said rods respectively and movable along the latterinto an interlocking relation with said lugs to lock said grid againstremoval fromI either of said rods.

7. The combination with a bank of grid lli) resistances andv commonsupporting rods therefor, said grids each having lugs with open slotsfor engagement with said rods, of a plurality of members surroundingeach of said rods and each being movable along its respective rod intoan interlocking relation With a lug of a grid to look such grid againstremoval, and means including parts on opposite sides of the bank ofgrids to con fine therebetween in interlocking relation all of said lugsand members.

8. The combination With a grid resistance and supporting means thereforincluding a rod, said grid having a lug with an open slot for engagementwith said rod and said lug having a shoulder concentric with said rod,of a Washer surrounding said rod and having an annular flange to overlapsaid shoulder on said lug for locking said grid on said rod subject torelease by relative m'cvement of said lug and member along said ro 9.The combination with a grid resistance and supporting rods therefor,said grid having lugs with open slots for engagement with said rods, ofmembers supported by said rods and having parts to be interlocked withparts of said lugs of said grid to lock the latter on said rods, saidinterlocking parts enabling release of said grid for removal by relativemovement of said lugs and members along said rods but said interlockingparts having overlap affording securement of said grid on said rods Witha loose assembly of said grid and members.

In testimony whereof, I aix my signature.

HARRY E. CAMPBELL.

